Method of and apparatus for extruding tubing



Dec. 13, 1960 A. GOLDSMITH E i-AL 2,964,178

METHOD OF AND APPARATUS FOR EXTRUDING TUBING Filed Jan. 10, 1950 2 Sheets-Sheet 1 as 34 %/l INVEN TOR. L an L Quasi my gas 6. l/cpym/ Dec. 13, 1960 A. L. GOLDSMITH ETAL METHOD OF AND APPARATUS FOR EXTRUDING TUBING Filed Jan. 10, 1950 Ila-5 .2 Sheets-Sheet 2 87: as w Ins-.5

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5M 1. Gums/711w M55 6 INK/1AM 7' 7' ORNE V United StatesPatent O METHOD OF AND APPARATUS FOR EXTRUDING TUBING Allen L. Goldsmith, 16 Scott Drive, and Charles E. Hickman, 316 S. Scott, Adrian, Mich.

Filed Jan. 10, 1950, Ser. No. 137,824

18 Claims. (Cl. 207-) This application relates to a method of and apparatus for extruding tubing, and has a particular reference to such a method and apparatus useful in connection with the manufacture of relatively thin walled, small diameter aluminum tubing, although the invention is not limited to use in connection with the manufacture of aluminum tubing. 7

At the present time considerable difficulty and expense are encountered in manufacturing commercially satisfactory thin walled metal' tubing due to the difliculty of maintaining relatively uniform wall thicknesses, and because of this it is customary at the present time to redraw aluminum tubing in order to obtain small diameter tubing of commercially satisfactory concentricity.

In addition, considerable ditficulty and expense are now encountered in connection with the manufacture of thin walled, small diameter aluminum tubing due to wear of the dies and the cores and the high pressures involved which cause the core to sink into the housing. Furthermore, dies now used are very expensive, the metal slug is hard to remove from the dies, and frequently the cores are bent when the butt is sheared due to the long, rigidly held core now conventionally employed.

This invention contemplates a method of and apparatus for manufacturing small diameter, thin walled aluminum tubing which makes it possible to obtain commercially satisfactory tubing without the necessity of a redrawing operation. Furthermore, the die construction contemplated by this invention is superior to that now employed and is, in addition, less expensive due to the unique construction of such dies embodying our invention. In addition, when using dies embodying our invention it is comparatively easy to remove the metal slug, and the likelihood of bending the core is considerably reduced due to the fact that this invention contemplates the use of a floating core.

A principal object of the invention, therefore, is to provide a new and improved apparatus for extruding thin walled, small diameter aluminum tubing.

- Another object of the invention is to provide an improved method of producing thin walled, small diameter aluminum tubing.

Another object of the invention is to provide a new and improved .method of and apparatus for producing thin walled, small diameter aluminum tubing on a commercially satisfactory basis without the necessity of redrawing such tubing.

Another object of the invention is to provide a new and improved die construction for extruding thin walled, small diameter aluminum tubing and which dies are cheaper in construction and will produce a better and more uniform tubing than dies now commercially in use.

Another object of the invention is to provide a new and improved die structure for extruding aluminum tubing which eliminates the necessity for accurately fitted parts and which employs a floating core.

, Another object of the invention is to provide a new andimproved process of extruding aluminum-tubing in which the pressure of the metal being extruded is employed to center the core with respect to the annular die ring, thereby making it possible to obtain a uniformly good grade of commercially satisfactory tubing without the necessity of redrawing operations.

Other and further objects of the invention will be apparent from the following description and claims and may be understood by reference to the accompanying drawings, of which there are two sheets, which by way of illustration show preferred embodiments'of the invention and what we now consider to be the best mode in which we have contemplated applying the principles of our invention. Other embodiments of the invention may be used without departing from the scope of the present invention as set forth in the appended claims.

In the drawings:

Fig. 1 is alongitudinal sectional view through the die parts of an apparatus embodying the invention;

Fig. 2 is a sectional view taken along the staggered line 22 of Fig. 1;

Fig. 3 is an elevational view of one face of the tube die housing; v 1 I Fig. 4 is a view similar to Fig. 1, illustrating a modified form of the invention;

Fig. 5 is a view similar to Fig. 1', illustrating'a modified form of the invention; A

Fig. 6 is a view similar to Fig. 1, illustratinga further modification; and 1 Fig. 7 is an elevational view, partially in section, of a plug used for aligning the core and annular die when the apparatus is initially set up.

As shownin Fig. 1, an apparatus for extruding tubing comprises a tube die housing or member 10, a tube die backer or member 12, a core 14, and a die member 30 associated with a containing cylinder 16 of a press. The

v backer 12 and housing 10 are suitably securely fixed as illustrated relative to each other and to the containing cylinder 16 in any conventional manner so that the billet 18 in the cylinder will flow under the influence of heat and pressure into the coalescence chamber 20.

The coalescence chamber 20 comprises an annular chamber formed by hollowed out portions of the backer 12 and the housing 10. The housing 10 is provided with a plurality of cylindrical passages 22 between the chamber 20 and the other end of the housing, such passages communicating with the interior of the containing cylinder 16. The passages are symmetrically arranged parallel to the axis of the chamber 20. As previously indicated, the containing cylinder 16 forms a part of a means for feeding aluminum to be extruded under pressure through the passages 22 into the chamber 20, and for this purpose a billet 18 of aluminum may be arranged in the cylinder and pressure applied to the billet by and through the piston block 24.

As is conventional in the art, the die parts, the billet, and the containing cylinder are maintained at suitable temperatures during the operation of the apparatus. The pressure applied to the billet to cause it to flow may be of the order of 100,000 lb. per square inch, but the pressure required is dependent to some extent upon the temperature to which the parts are heated.

The face 26 of the tube die backer which'forms one wall of the chamber 20 is provided with a circular openiug'ZS disposed concentrically relative to the axis of the chamber 20 and through which the aluminum to be However, an.

the opening 28 and forms a die for determining the out-' side diameter of the tubing to be extruded. Whil'eth'e die member 30 is seated in a recess in the face 26, it may have a loose or floating fit therein so that it is free to shift in a plane normal to the axis of the chamber 20.

The housing 10 is provided with a socket 32 which loosely receives the base 34 of the core 14 so that the core has a loose or floating support on the hub 36 of the housing 10. The core 14 is disposed on the axis of the chamber 20 and projects into the annular die 30 in spaced relation therewith so as to form an annular opening between the core 14 and the die 30.

The aluminum to be extruded flows from the containing cylinder 16 through the passages 22 into the chamber 20 and completely fills the same. In the chamber 20 the aluminum coalesces and completely fills the chamher and surrounds the core 14, and aluminum flows between the core 14 and the die 30 to form seamless extruded tubing indicated at 38.

While the core 14 has a loose fit in the socket 32, it is held in place by the pressure which the aluminum in chamber 20 exerts upon the diiference in cross sectional area between the base 34 and the stem 40 of core 14.

The pressure exerted by the aluminum in chamber 20 as it flows through the annular opening between the core 14 and the die member 30 tends tocause the core 14 to center itself in said annular opening. If the die member 30 is free to float, the-pressure exerted by the aluminum in the chamber 20 as it flows through the annular opening between core 14 and die 30 will also tend to cause die 30 to center itself with respect to core 14. The core 14 may, if desired, likewise be formed of material such as tungsten carbide.

In the modification illustrated in Fig. 4, the construction is the same except that the core 114 is mounted somewhat differently. In Fig. 4 the socket 132 for the base 134 of the core faces the containing cylinder 16 and the base 134 of the core has a loose fit in the socket 132. However, the bottom wall 136 of the socket is normal to the axis of the chamber, and the core base 134 seats on the Wall 136. The shank 138 of the core projects loosely through an opening in the hub 140 of the housing 10 and into the opening in the die member 30. The fit between the shank 138 and the hole in the hub- 140 through which it extends is sufliciently loose so as to permit the core 114 to float and center itself with respect to the opening in the die 30 under the pressure of the aluminum being extruded.

The die 30 (Fig. 4) is a floating die member, although it is not necessary that both the die 30 and the core float. It is sufficient if one floats with respect to the other, and to this end either the die 30 or the core may float. While the cores in both modifications float, they nevertheless are securely held against axial movement toward the die member 30: in the case of Fig. 1, by the pressure of the aluminum in the chamber 20, and in the case of Fig. 4, by the pressure of the billet 18 which holds the base 134 of the core seated on the bottom wall 136 of the socket.

In the modification illustrated in Fig. the construction is the same as in Fig. 1 except that a pressure plate 42 has been arranged to partially cover the die member 30, allowing suitable clearance so that the thrust exerted by the pressure of the metal in the chamber 20 will be withheld from the surfaces of the die member 30 normal to the axis of the chamber thereby permitting the die member to move with more freedom. The pressure plate may be made so as to relieve the die member 30 of up to 90% of the pressure exerted thereon by the material in the chamber 20.

In the modification shown in Fig. 6 the construction is similar to Fig. 1 except that the core 148 has been designed to permit more flexible movement. In Fig. 6 the core 148 has a ball end 156 which fits loosely in socket 162 and is held in place by a retainer ring 152 which rests against the shoulder 153. The stem 150 of 4 core 148 is a loose fit in ring 152, thereby permitting the core to concentrically align itself more freely with die member 30. The frictional drag of the aluminum in chamber on stem 1S0 holds ball 156 against ring 152 while the pressure which the aluminum in chamber 20 exerts upon ring 152 holds it against shoulder 158, thereby holding the core 148 against movement toward die member 30.

With the die construction illustrated it is easy to remove the core, and also the metal slug which is left in the housing 10 for inspection and replacement of worn parts.

According to present practice it is not economically I feasible or mechanically practical to produce seamless aluminum tubing under one inch in diameter and with less than .050 inch wall thickness without redrawing, whereas we are now producing and marketing one-fourth inch outside diameter seamless aluminum having a wall thickness of .040 inch with a tolerance of plus or minus .004 inch by the use of our invention. While one-fourth inch diameter tube is the smallest diameter so far produced, there is no reason to suppose that smaller diameters and wall thicknesses below .040 inch may not be produced by our invention.

When the apparatus is initially set up for extruding tubing it is preferable to mechanically position the core concentrically relative to the die member 30, and this may be accomplished with the use of a set up plug 200 like that shown in Fig. 7. This plug has a stem 202 which accurately and closely fits within the opening in the die member 30 and is provided with a counterbore 204 for accommodating the end of the core, the counterbore 204 being concentric relative to the stem 202 so that with the core projecting into the counterbore 204 and with the stem 202 projecting through the opening in the die member 30, the core will be accurately positioned concentrically relative to the die member 30. Thereafter the die housing 10 and the chamber 20 are cast full of the aluminum so as to freeze or set the core relative to the die member 30.

After the die housing 10 and the die backer 12 with the core and die member 30 operatively assembled therewith are operatively associated with the containing cylinder 16 and extrusion pressure applied to the billet 18, the metal which was cast into the die housing 10 and the chamber 20 will be extruded by the billet as it flows through the housing 10 and the chamber 20 and through the annular opening between the core and the die member 30. The metal which was cast into the die housing 10 and the chamber 20 to initially position the core and the die member 30 will be scrapped and the metal of the billet 18 in being extruded will have uniform wall thickness, and the pressure exerted by the aluminum in the chamber 20 as it flows through the annular opening between the core and the die member 30 will maintain the core and die member concentric relative to each other. The plug 200 will be pushed out of the die opening in the die member 30 by the metal cast in the chamber 20 as soon as it starts to be extruded through the die member 30 since the plug 200 is frictionally held in position.

While we have illustrated and described preferred embodiments of our invention, it is understood that these are capable of modification, and we therefore do not wish to be limited to the precise details set forth but desire to avail ourselves of such changes and alterations as fall within the purview of the following claims.

We claim:

1. Apparatus for extruding metal tubing comprising a tube die housing, a tube die member, and a core constructed and arranged so as to be axially immovable during an extruding operation, a coalescence chamber adja cent said die member, a transversely extending fixed part of said housing being provided with a passage through which metal in a solid state is supplied to said. chamber for extrusion therefrom, an unobstructed cylinder communicating with said passage and otherwise separated from said chamber by said part, and adapted to hold a solid billet of metal to be extruded, means, independent of said core, and including a piston which extends completely across said cylinder, operable for forcing the metal, of a solid billet in said cylinder, to flow through said passage into said chamber and to coalesce around said core and to be extruded as metal tubing from said chamber, said tube die member being provided with a die opening communicating with said chamber for determining the outside of the tubing as it is extruded from said chamber, said transversely extending fixed part of saidihousing having a socket, one end of said core being loosely received in said socket so that said one end of said core is loosely supported and centered by said housing part, the other end of said core being free and projecting through said chamber freely into said die opening for determining the inside of said tubing as it is extruded from said chamber, the supporting arrangement between said one end of said core and said housing being such that said core is free to float transversely relative to said die member, said core during extrusion being engaged by the metal in said chamber and the free end of said core being otherwise unrestrained against limited movement transversely of said chamber except by said metal therein so that the pressure thereof on said free end of said core acts to center the free end of said core during an extruding operation relative to a predetermined axis passing through said die opening.

2. Apparatus according to claim 1 wherein said core is provided with a transversely extending surface exposed to and engaged by the metal in said chamber so that the pressure thereof on such surface during an extruding operation holds said core against axial movement relative to said die member during said extruding operation.

3. Apparatus for extruding metal tubing comprising a tube die housing, a die member, and a core, a coalescence chamber adjacent said die member, a transversely extending fixed part of said housing being provided with a metal supply passage to said chamber, an unobstructed cylinder communicating with said passage and otherwise separated from said chamber by said part, and adapted to hold a solid billet of metal to be extruded, means, independent of saidoore, and including a piston which extends completely across said cylinder, operable for forcing the metal, of a solid billet in said cylinder, to flow through said passage into said chamber and to coalesce around said core and to be extruded as metal tubing from said chamber, the base of said core being centered by said housing part, said die member being disposed in said chamber and provided with a die opening from said chamber for determining the outside of the tubing as it is extruded from said chamber, one end of said core freely projecting into said die opening for determining the inside of said tubing as it is extruded fromsaid chamber, said die member being mounted in said chamber so that it is free to move transversely relative to said one end of said core andbeing engaged by the metal in said chamber so that the pressure thereof on said die member during an extruding operation acts to center said die member relative'to the free end of said core during an extruding operation, said core being provided with an enlargement by means of which said core is restrained against axial movement through said die opening during an extruding operation.

4. Apparatus according to claim 3 including a pressure plate arranged to partially cover said die member with a slight clearance therebetween so that the surfaces of said die member normal to the axis of said chamber are largely relieved of the thrust exerted by the metal in said chamber during an extruding operation.

5. Apparatus for extruding metal tubing comprising a first tube die member, a second tube die, a coalescence chamber therebetween, and a core in said chamber, a

6 transversely extending fixed part of said first member being provided with a materialsupply passage into said chamber and a socket, means independent of said core for feeding metal in a solid state under pressure through said passage into said chamber so as to coalesce said metal around said core and to extrude metal tubing from said chamber, said second tube die being provided with adie opening communicating with said chamber for determining the outside of the tubing as it is extruded from said chamber, one end of said core being loosely received in said socket so that said end of said core is loosely supported and centered by said part of said first member and the other end of said core projecting freely into said die opening for determining the inside of said tubing as it is extruded, said core being exposed to and engaged by the metal in said chamber and the free end of said core being otherwise unrestrained during extrusion against limited movement transversely of said cham-, ber except by said metal therein so that the pressure thereof on said free end of said core during an extruding operation acts to center the free end of said core relative to a predetermined axis passing through said die opening, and means restraining said core against axial movement through said die opening during an extruding operation.

6. Apparatus according to claim 5 wherein said lastmentioned means comprise a transversely extending surface on said core facing saiddie member and exposed to and engaged by the metal in said chamber so that thepressure thereof on such surface during an extruding operation holds said core against axial movement relative to said die member during said extruding operation.

7. Apparatus according to claim 5 wherein said second tube die includes an annular die member defining said die opening and constructed and arranged so as to be free to shift laterally within limits relative to said core under the pressure of the material in said chamber, during an extruding operation. 7

8. Apparatus for extruding metal tubing'comprising die parts formed and arranged to provide a coalescence chamber having an opening therefrom and an inlet thereto through which metal in a solid state is supplied under pressure to said chamber for extrusion therefrom through said opening in the form of metal tubing, a die member disposed around said opening for determining the out-' side of the tubing as it is extruded from said chamber, a core member in said chamber around which the metal supplied under pressure to said chamber coalesces, said core having one end freely projecting into the opening of said die member for determining the inside of the tubing as it is extruded from said chamber, one of said members being loosely supported by said die parts for limited movement transverse of the axis of said chamber and exposed to'the metal in said chamber so that the of said core member and including a piston which extends completely across said cylinder, operable for forcing the metal, of a solid billet in said cylinder, to flow through said inlet into said chamber and to coalesce around said core and to be extruded as metal tubing from said chamber.

9. Apparatus for extruding metal tubing comprising die parts formed and arranged to provide a coalescence chamber, an opening therefrom and an inlet thereto through which metal in a solid state is supplied under pressure to said chamber for extrusion therefrom through; said opening in the form of metal tubing, said inletoom prising a plurality of passages arranged symmetrical with respect to the axis of said chamber, an annular die member disposed around said opening for determining the outside of the tubing as it is extruded from said chamber, a core member in said chamber around which the metal supplied under pressure to said chamber coalesces, said core member being constructed and arranged so as to be axially immovable relative to said annular die member during an extruding operation and freely projecting into the opening of said annular die member for determining the inside of the tubing as it is extruded from said chamber, one of said members being loosely supported by said die parts for limited movement transversely of the axis of said chamber and exposed to the material in said chamber and being otherwise unrestrained against limited movement transversely of said chamber except by said metal therein so that the pressure thereof to which said one of said members is subjected during an extruding operation acts to center said core member and said die member relative to each other during an extruding operation, an unobstructed cylinder communicating with said passages and otherwise separated from said chamber, and adapted to hold a solid billet of metal to be extruded, means, independent of said core member and including a piston which extends completely across said cylinder, operable for forcing the metal, of a solid billet in said cylinder, to flow through said passages into said chamber and to coalesce around said core and to be extruded as metal tubing from said chamber.

10. Apparatus for extruding metal tubing comprising die parts formed and arranged to provide a coalescence chamber, a die opening therefrom andan inlet thereto through which metal in a solid state is supplied to said chamber for extrusion therefrom through said opening in the form of metal tubing, said die opening determining the outside of the tubing as it is extruded from said chamber, a core member in said chamber around which the metal supplied to said chamber ooalesces and freely projecting into said die opening for determining the inside of the tubing as it is extruded from said chamber, one of said die parts being provided with a socket in which one end of said core member is loosely received so that said core member is loosely supported by said die parts for limited movement transversely of the axis of said chamber, said core during extrusion being exposed to the metal in said chamber and the free end of said core being otherwise unrestrained against limited movement transversely of said chamber except by said metal therein so that the pressure thereof on said core member during an extruding operation acts to center the free end of said core member relative to a predetermined axis passing through said die opening, said core member being constructed and am ranged so as to be axially immovable during an extruding operation, and means independent of said core member for supplying metal in a solid state to said coalescence chamber through the inlet thereto.

11. Apparatus according to claim 10 in which the core member is constructed and arranged so that the pressure of the metal to be extruded in said chamber, counteracts the drag effect of the metal being extruded on the core member which tends to propel the core member through the die opening, so that such pressure holds said core member axially immovable relative to said annular opening in said die during an extruding operation.

12. Apparatus according to claim 10 in which said core member is provided with a transversely extending surface engaged by the metal in said coalescence chamber so that the pressure thereof on such surface during an extruding operation holds said core against axial movement toward and through said die opening during said extruding operation.

13. Apparatus for extruding metal tubing comprising a tube die housing, a tube die backer, and a core, said tube die housing cooperating with said tube die hacker to provide a'coalescence chamber, said housing being provided with a material supply passage to said chamber, an unobstructed cylinder communicating with said passage and otherwise separated from said chamber, and adapted to hold a solid billet of metal to be extruded, means, independent of said core and including a piston which extends completely across said cylinder, operable for forcing the metal, of a solid billet in said cylinder, to flow through said passages into said chamber and to coalesce around said core and to be extruded as metal tubing from said chamber, said tube die backer being provided with a die opening for determining the outside of the tubing as it is extruded, said housing having a socket facing 'said die opening and disposed between said cylinder and chamber, said core having a base loosely arranged in said socket and a stem projecting freely into said die opening for determining the inside of said tubing as it is extruded, a surface of said base being exposed to and extending transversely of said chamber and the opposite surface of said base being shielded by said housing, said core being subject to the pressure of the metal in said chamber during an extruding operation so that the pressure thereof on said stem acts to center the stem of said core relative to a predetermined axis passing through said die opening, and the pressure thereof on said base holds said core against axial movement relative to said die opening during such extruding operation.

14. Apparatus according to claim 13 including a retainer ring covering said socket and subject to the pressure of the metal in said chamber during an extruding operation, said ring having the stem of said core loosely projecting therethrough and cooperating with said base to retain said core against axial movement through said die opening during an extruding operation.

=15. Apparatus for extruding metal tubing comprising a first tube die member, a second tube die member, a coalescence chamber therebetween, and a core in said chamber, said first die member having a socket in which one end of said core is loosely received so that said core is loosely supported in said coalescence chamber, means independent of said core for feeding metal in a solid state under pressure into said chamber so as to coalesce said metal around said core and to extrude metal tubing from said chamber, said second tube die member being provided with a die opening communicating with said chamber for determining the outside of the tubing as it is extruded from said chamber, the other end of said core projecting freely into said die opening for determining the inside of said tubing as it is extruded, said core being provided with a transversely extending surface facing said die opening and exposed to and engaged by the metal in said chamber so that the pressure thereof on such surface during an extruding operation forms the sole means for holding said core against axial movement through said die opening and relative to said die members during said extruding operation.

16. That method of extruding metal tubing wherein a core member projects into the opening in an annular die member and wherein said members are axially movable relative to each other during an extruding operation and one of said members is free to shift transversely relative to the axis thereof, which consists of heating and subjecting a billet of metal in a solid state to pressure so as to force the metal thereof to flow and coalesce under pressure around said core member and against said die member and to flow through the space therebetween, positioning said core member and die member in a predetermined position relative to each other solely by utilizing the pressure exerted by said metal on said core member during an extruding operation, and holding said core member against axial movement toward and through said die member during an extruding operation solely by utilizing the back pressure exerted by said metal during an extruding operation on said core member.

17. That method of extruding metal tubing wherein a core member freely projects into the opening in an annular die member and wherein one of said members is free to shift transversely relative to the axis of the other, which consists of heating and subjecting a billet of metal in a solid state to pressure so as to cause it to flow and coalesce around said core member and against said die member so as to extrude said metal through the space therebetween, and utilizing the pressure exerted by said metal during said extruding operation to center said core and die members relative to each other and to hold said core member against axial movement toward and through said die member.

18. That method of extruding metal tubing wherein a core member projects into the opening in an annular die member and wherein said members are axially immovable relative to each other during an extruding operation and one of said members is free to shift transversely relative to the axis thereof, which consists of heating and subjecting a billet of metal in a solid state to pressure so as to force the metal thereof to flow and coalesce under pressure around said core member and against said die member and to flow through the space therebetween, and

10 holding said core member against axial movement toward and through said die member during an extruding operation solely by the pressure exerted by said metal during an extruding operation on said core member.

References Cited in the file of this patent UNITED STATES PATENTS Re. 82 Hansom Mar. 14, 1846 8,943 Tatharn May 11, 1852 1,084,881 Gahlen Jan. 20, 1914 1,285,328 Neuberth Nov. 19, 1918 1,720,722 Dean July 16, 1929 1,847,365 Skinner Mar. 1, 1932 2,366,344 McFadden Jan. 2, 1945 FOREIGN PATENTS 437,075 Great Britain July 1, 1935 613,057 Great Britain Nov. 22, 1948 865,463 France May 24, 1941 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent N-oa 2364 178 December l3 1960 Allen Lo Goldsmith et a1 It is hereby certified that error appears in the above numbered patent requiring correction and 'that the said Letters Patent should read'as corrected below.

Column 8, line 58 for "movable" read irmnovable Signed and sealed this 29th day of August 1961.,

(SEAL) i Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

